#ifdef LINUX_HOST
#include <vmlinux.h>
#include <bpf/bpf_core_read.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#else
#include "vmlinux.h"
#include "bpf_core_read.h"
#include "bpf_helpers.h"
#include "bpf_tracing.h"
#endif // LINUX_HOST
#include "funclatency.h"
#include "bits.bpf.h"

const volatile pid_t targ_tgid = 0;
const volatile int units = 0;
const volatile bool filter_cg = false;

struct {
    __uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
    __type(key, u32);
    __type(value, u32);
    __uint(max_entries, 1);
} cgroup_map SEC(".maps");

/* key: pid.  value: start time */
struct {
    __uint(type, BPF_MAP_TYPE_HASH);
    __uint(max_entries, MAX_PIDS);
    __type(key, u32);
    __type(value, u64);
} starts SEC(".maps");

__u32 hist[MAX_SLOTS] = {};

static __always_inline void entry(void)
{
    u64 id = bpf_get_current_pid_tgid();
    u32 tgid = id >> 32;
    u32 pid = id;
    u64 nsec;

    if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
        return;

    if (targ_tgid && targ_tgid != tgid)
        return;
    nsec = bpf_ktime_get_ns();
    bpf_map_update_elem(&starts, &pid, &nsec, BPF_ANY);
}

SEC("fentry/dummy_fentry")
int BPF_PROG(dummy_fentry)
{
    entry();
    return 0;
}

SEC("kprobe/dummy_kprobe")
int BPF_KPROBE(dummy_kprobe)
{
    entry();
    return 0;
}

static __always_inline void exit(void)
{
    u64 *start;
    u64 nsec = bpf_ktime_get_ns();
    u64 id = bpf_get_current_pid_tgid();
    u32 pid = id;
    u64 slot, delta;

    if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
        return;

    start = bpf_map_lookup_elem(&starts, &pid);
    if (!start)
        return;

    delta = nsec - *start;

    switch (units) {
    case USEC:
        delta /= 1000;
        break;
    case MSEC:
        delta /= 1000000;
        break;
    }

    slot = log2l(delta);
    if (slot >= MAX_SLOTS)
        slot = MAX_SLOTS - 1;
    __sync_fetch_and_add(&hist[slot], 1);
}

SEC("fexit/dummy_fexit")
int BPF_PROG(dummy_fexit)
{
    exit();
    return 0;
}

SEC("kretprobe/dummy_kretprobe")
int BPF_KRETPROBE(dummy_kretprobe)
{
    exit();
    return 0;
}

char LICENSE[] SEC("license") = "GPL";
